2019-01-14 General Committee Agenda - Attachment 3 to Item 2 - Monitoring of Noosa River Oyster Reefs Nov 2018

We identified significant oyster settlement during both monitoring events on both necklaces
and in the oyster restoration unit bags (Figure 19, Figure S1, Table 4, Table 5). Overall, we
identified an average of 387.5 spat/m2 in May 2018, 306.1 oysters/m2 in November 2018,
and 349.9 oysters/m2 across both monitoring events (Table 4). Whilst we identified some
changes in the densities of oysters at specific restoration sites (Figure S1, Table 5), with
some sites showing increased oyster density between sampling events, and others lower
oyster density, the overall pattern was for a reduction in oyster density between monitoring
events 1 and 2 (Table 4). This change was, however, offset by a significant change in the
size-frequency distribution of oyster shells on the reefs (Figure 20, Figure S2). Here oysters
increased in size from 14.3 mm (+/- 6.5 mm SD) in May 2018, to 19.1 mm (+/- 8.9 mm SD)
in November 2018. Consequently, it is likely that intermediate sized oysters (6-15 mm in
length) in May 2018 grew to the larger sizes (i.e. <30 mm) by November 2018, and that the
smaller oysters (<6mm) either grew to an intermediate size, or did not survive the winter.
Consequently, despite a reduction in overall average density, this was offset by a larger
average oyster size during the second monitoring event.




Figure 19 Example images of juvenile oysters growing on shells collected from within the
oyster reef restoration units.

Table 4 List of oyster quantification methods, and the average densities (with standard
deviations) of oysters during both monitoring events, and for all monitoring events in 2018.
                Monitoring event 1           Monitoring event 2           Overall (both events)
                           2                            2                              2
            Average (spat/m )   StDev    Average (spat/m )   StDev     Average (spat/m )    StDev
Necklaces                543.7   643.5                493.9   513.4                  525.8   599.3
Bags                    272.9    413.3                230.9   438.2                 251.9   425.9
All                     385.7    537.7                306.1   475.1                 349.9   511.7




                                                                                               22